The present invention relates to a new and improved construction of the cutting member of a flail for use in a rotary impact mechanism of a comminuting machine.
In its more particular aspects, the present invention specifically relates to the new and improved construction of the cutting member which constitutes a cast body defining a cutting head exerting a comminuting action upon material impacted by the cutting head of the flail. The cutting head preferably has a substantially triangular cross-section and defines a cutting edge which extends substantially parallel to the rotational axis of the rotary impact mechanism once the cutting member is installed in the rotary impact mechanism. The cutting head may be provided with a wear-resistant hard metal extending along the cutting edge.
An example of the construction of a flail of the aforementioned type is known from German Published Patent Application No. 3,545,708 filed on Jun. 25, 1987, of the applicant of the instant application. The flail serves for comminuting material in comminuting machines in which the flail is mounted between adjacent rotor discs of a rotor body which is the main component of a rotary impact mechanism. The cutting member of the flail is exchangeably mounted at a carrier which is pivotably mounted between the adjacent rotor discs such that the carrier is pivoted under the action of centrifugal forces into an operative position during rotation of the rotor body. In such operative position, the cutting member protrudes from the circumference of the rotor body. The cutting member defines a cutting edge which extends substantially parallel to the rotational axis of the rotary impact mechanism.
Flails of the aforementioned type are also used in a comminuting machine or composting equipment such as known, for example, from U.S. Pat. No. 4,852,816, granted on Aug. 1, 1989, to the applicant of the instant application. In such machine, organic or wood waste originating in forestry, municipality or building operations is comminuted and deposited in stacks or pits for composting. A trough-shaped container receives the material to be comminuted, for example, by means of a shovel loader. Infeed means are provided in the form of an infeed conveyor which is located above the bottom of the container and feeds the material to a rotary impact mechanism which drives the infed material through an entrance gap defined between an impact ledge and the rotating flails of the rotary impact mechanism. The rotary impact mechanism is formed by a plural number of rotor discs which are mounted at a common axle, and the carriers of the flails are pivotably mounted between adjacent pairs of the rotor discs. Cutting heads of the flails protrude beyond the circumference of the rotating discs and act upon the material to be comminuted during rotation of the rotary impact mechanism. The impact ledge is followed by retainer claws which extend between adjacent ones of the rotating flails for comminuting the material which has been forced through the entrance gap. An impact plate follows the retainer claws and has teeth protruding toward the rotating flails and cooperating therewith for further comminuting the material prior to its discharge through a discharge opening from a rear part of the container.
In a further development (Doppstadt shredder, type AK 330) of the aforementioned comminuting machine, the infeed means further include an intake roll which bears upon the infed material from above. The entrance gap is followed by an impact plate containing two plate sections. The two plate sections are arranged at an angle with respect to each other so that the impact plate extends along an upper part of the cylindrical action area of the rotary impact mechanism. Teeth protrude from the impact plate toward the rotary impact mechanism and are arranged in parallel rows transverse with respect to the rotational direction of the rotary impact mechanism, the rows of teeth being transversely offset from each other. There is thus defined a throughpass gap through which the incoming material is forced under the action of the rotating flails and subjected to comminuting action. Like in the aforementionned comminuting machine, the rotating flails are pivotably mounted between adjacent discs in rows which extend in axial direction of the rotary impact mechanism and which are circumferentially spaced from each other. The axial rows are offset from each other in axial direction so that the rotating flails define a substantially uninterrupted cylindrical area of action. Following the impact plate, the comminuted material is either discharged through the rear discharge opening of the container or subjected to further comminution by further comminuting means which follow the impact plate and cover the entire discharge opening or a part thereof and which cooperate with the rotating flails.
In both of the aforementioned comminuting machines the impact plate as well as the further comminuting machines are pivotably supported so as to pivot away from the rotating flails in the event that the infed material contains pieces of material which do not disintegrate under the action of the rotating flails in cooperation with the impact plate. Also, the flails are pivotably mounted such as to pivot back between the associated adjacent discs in the event that the rotating flails impact at such non-disintegratable pieces of material. The rotating flails and the impact plate are thus prevented from damage by the pieces of non-disintegratable material.
In these constructions, the cutting member and particularly the cutting edge of the cutting head, is subject to wear due to the comminuting action on the material to be comminuted. In order to reduce such wear and thus increase the useful service life of the cutting member, it has become known to provide the cutting edge with wear-resistant hard metal. As a result of the vigorous interaction with the infed material to be comminuted, even the hard metal is subject to wear and it may even happen that the hard metal is broken off from the cutting edge which will render the flail inoperative.